We propose an analysis of mental health and mental illness in the aged by studies of behavior, some aspects of cerebral neurophysiology and imaging of brain structure in vivo. Our objectives are (1) the analysis of the value of various behavioral and biomedical factors in predicting the development of severe senile dementia and (2) a study of the interrelationships of behavioral and biomedical data derived from serial testing of the aged. One hundred subjects aged 65 to 75, fifty thought to be in early phase of senile dementia and fifty matched controls, will be studied serially over a two year period with medical evaluation, clinical neurologic assessment, psychometric studies, advanced analysis of the visual evoked response (VER) and an original adaptation of computerized cranial tomography (CT). Data analysis will reveal (1) the pedictive value when performed serially in the same patients of the tests (alone and in combination) regarding the clinical course of senile dementia as opposed to normal aging and (2) the interdependencies of the various clinical, behavioral, physiological and brain structural data. Subjects ill be followed thereafter until autopsy when half of the brain will be prepred for neuropathological examination and half preserved for future morphologic, chemical and other studies.